Electrochemical Determination of L-Glutamate on a Carbon-Containing Electrode Modified with Gold by Voltammetry

In this paper the L-glutamate electrochemical behavior on a carbon-containing electrode modified with gold in simulated solutions by cyclic voltammetry have been studied. The analytical signal of glutamate reduction at the potential of -0.8 V in pH 9.19 has been found. It has been determined that the cathodic reduction of glutamate is irreversible and mainly controlled by diffusion in the reduction electrode process of glutamate. The conditions for glutamate determination in simulated solutions by voltammetry have been found. The plots of current versus concentration present a linear behavior from 3.2·10{-4} to 2.5·10{-3} M. The detection limit is 4.4 10{-5} M. The glutamate determination in simulated solutions has resulted in acceptable deviation from the stated concentration where relative errors are -2.7 to +2.6%

Determination of Total Antioxidant Content in Various Drinks by Amperometry

In the present work the total content of phenolic antioxidants in juice of some fruit and vegetables, in wines, water extracts of tea and herb were measured by amperometry. Efficiency of the method allowed determining the total antioxidant content in their binary and multimixes, including processes of frosting-defrosting and juice diluting as well. The deviation of experimentally received values of the total antioxidant content in some drink mixes from the values calculated proceeding from the additivity principle of the antioxidant content in separate drinks has been revealed

Voltammetric Sensor for Total Cholesterol Determination

We report on a voltammetric sensor for the detection of total cholesterol. The sensor was fabricated by co-immobilization of two enzymes: cholesterol oxidase (ChOx) and horseradish peroxidase (HRP) on porous graphite. The electrochemical behavior of the sensor was studied with the use of linear sweep voltammetry. It has been shown that the sensor has high stability and high sensitivity (16 muA mM{-1} cm{-2}). The biosensor exhibited a wide linear range up to 300 mol/dm3 in a condition close to physiological (pH=6.86). Besides, the interferences of some key analytes containing in the blood were studied. As a matter of fact, making a fabricated sensor is rather promising for using in clinical practice

Investigation of Coenzyme Q[10] by Voltammetry

A simple, accurate and rapid voltammetric method has been developed for the quantitative determination of coenzyme Q[10]. Studies with direct current voltammetry were carried out using a glassy carbon electrode (GCE) in a phosphate buffer solution (pH 6.86). A well-defined oxidation peak of CoQ[10] was obtained at -0.600 V vs Ag/AgCl. The magnitude of the oxidation peak current has been found to be related to the concentration of the coenzyme over the range of (2.0x10{-5} to 2.0x10{-4} M) (r=0,991). Antioxidant activity of CoQ[10] was investigated

The Study of Redox Electrode Processes of Sulfur-Containing Compounds by Voltammetry

In this work the general case of quasi-reversible redox electrode processes of thiol compounds proceeding on a mercury-film electrode via a CE (chemical-electrochemical) mechanism has been revealed and investigated by voltammetry. The quantitative criteria for correlation between theory and experiment corresponding to a CE mechanism and new approach for estimating the kinetic parameters of the preceding chemical reaction have been suggested

Fluorescence Analysis of E. coli Bacteria in Water

The fluorescence analysis of Escherichia coli (E. coli) bacteria was done. It has been established that a luminescent signal from the one of metabolites (reduction form of nicotinamide adenine dinucleotide, NADH) can be adopted as a vitality indicator of the bacteria. This signal was chosen as an analytical signal. It was determined that the nature of this signal is fluorescence. In order to eliminate influence of the light scattering on this fluorescence signal optimal conditions were chosen

Label-Free Electrochemical Biosensors for the Determination of Flaviviruses: Dengue, Zika, and Japanese Encephalitis

A highly effective way to improve prognosis of viral infectious diseases and to determine the outcome of infection is early, fast, simple, and efficient diagnosis of viral pathogens in biological fluids. Among a wide range of viral pathogens, Flaviviruses attract a special attention. Flavivirus genus includes more than 70 viruses, the most familiar being dengue virus (DENV), Zika virus (ZIKV), and Japanese encephalitis virus (JEV). Haemorrhagic and encephalitis diseases are the most common severe consequences of flaviviral infection. Currently, increasing attention is being paid to the development of electrochemical immunological methods for the determination of Flaviviruses. This review critically compares and evaluates recent research progress in electrochemical biosensing of DENV, ZIKV, and JEV without labelling. Specific attention is paid to comparison of detection strategies, electrode materials, and analytical characteristics. The potential of so far developed biosensors is discussed together with an outlook for further development in this field

Correlation between Temperature Setting and DCS Complex Peak Energy and in ROMP of Dicyclopentadiene

Polydicyclopentadiene is one of the most interesting advanced polymers. After ring open metathesis polymerization (ROMP) by using second generation Grubbs catalyst, we obtain a crosslinked polymer with good mechanical properties. Heating is used to initiate the polymerization process as well as to obtain a higher degree of crosslinking between the polymer chains. We try to analyze the correlation between second stage heating and the degree of cross-linking by using DSC-analysis. DSC analysis shows us a complex exothermic peak after glass transition temperature and this peak area was analyzed

A Laser Reduced Graphene Oxide Grid Electrode for the Voltammetric Determination of Carbaryl

Laser-reduced graphene oxide (LRGO) on a polyethylene terephthalate (PET) substrate was prepared in one step to obtain the LRGO grid electrode for sensitive carbaryl determination. The grid form results in a grid distribution of different electrochemically active zones affecting the electroactive substance diffusion towards the electrode surface and increasing the electrochemical sensitivity for carbaryl determination. Carbaryl is electrochemically irreversibly oxidized at the secondary amine moiety of the molecule with the loss of one proton and one electron in the pH range from 5 to 7 by linear scan voltammetry (LSV) on the LRGO grid electrode with a scan rate of 300 mV/s. Some interference of the juice matrix molecules does not significantly affect the LSV oxidation current of carbaryl on the LRGO grid electrode after adsorptive accumulation without applied potential. The LRGO grid electrode can be used for LSV determination of carbaryl in fruit juices in the concentration range from 0.25 to 128 mg/L with LOD of 0.1 mg/L. The fabrication of the LRGO grid electrode opens up possibilities for further inexpensive monitoring of carbaryl in other fruit juices and fruits

Water Purification with Natural Sorbents: Effect of Surface Modification with Nano-structured Particles

Modified nanostructured sorbents are widely used in water treatment processes. In this work, aluminum and iron particles prepared by electro-spark dispersion have been applied as modifiers. Zeolite samples from "Holinskoe" mineral deposit (Russia, Republic of Buryatia), with a size smaller than 0.1 mm, have been modified with aluminum and iron particles, using a sol-gel process. The properties of the modified materials have been determined by means of sorption test, when removing ions Pb{2+}, Fe{3+} and Cd{2+} from the model solutions in static conditions. Using the method of thermal desorption of nitrogen (BET) it has been shown that increasing the iron content in the samples of nanostructured modified sorbents does not affect the increase in specific surface area and pore volume of the samples. Ions concentrations have been analyzed by stripping voltammetry and photocolorimetry. As a result, modified sorbents revealed a high efficiency sorption of heavy metals